The present invention relates to a composite structure of different materials, such as metals, ceramic materials, plastic materials and/or carbon or a composite structure of the same material.
It is generally known to join together members of different materials to form a composite structure having high chemical and mechanical properties, such as corrosion resistance, abrasion resistance, heat resistance and the like. Generally, a joining method that employs a mechanical joining process, such as thermal shrinkage fit or fit, or a bonding process using an adhesive is used to join together members of different materials, such as a metal member, and a ceramic or sintered member that is brittle but has high corrosion resistance and abrasion resistance.
The mechanical joining process for forming a composite structure by joining together mating members requires precision machining for shaping the mating members to avoid breakage of the mating members by stress concentration due to local contact forming between the mating members or difference in thermal expansion coefficient between the mating members. Therefore, the costs of forming the composite structure are high or working temperature range for the composite structure is limited.
Although the bonding process using an adhesive places some restrictions on working temperature range for the composite structure, the bonding process is easy to carry out and the costs of forming the composite structure by the bonding process are low. Therefore, the bonding process using an adhesive has become prevalent in recent years with the progress of adhesives. However, although the adhesive is capable of withstanding a high stationary load, the adhesive is frail under an impulsive load. In some cases, the composite structure is subject to fatal damage when an adhesive layer bonding the mating members together is broken by an impulsive load. Particularly, since the toughness of a ceramic member is low, when two mating members are separated due to the failure of the adhesive bonding the two mating member together, there is a possibility that the ceramic member breaks and, if the ceramic member is a rotating member, fragments of the broken ceramic member are scattered around.
It is an object of the present invention to overcome the disadvantages of the joining method of joining together members of different materials or the same material drastically and to obtain economically a strong composite structure excellent in corrosion resistance, abrasion resistance, heat resistance and the like.
To achieve the object, the present invention provides a composite structure comprising: first and second members combined and joined together, wherein the first member has a protruding part expanding toward its extremity, the second member has a concave part defining a space of a shape corresponding to that of the protruding part of the first member and capable of forming a predetermined clearance between the protruding part of the first member and the concave part of the second member when the first and the second members are combined, a minimum inside diameter of the concave part is greater than a maximum outside diameter of the protruding part and a wedge is inserted into the clearance between the protruding part of the first member and the concave part of the second member so that the first and the second members are prevented from being separated from each other.
In this composite structure, the clearance into which the wedges have been inserted, may be filled up with a filler.
In this composite structure, one of the first and the second member may be formed of a nonmetallic material and the other may be formed of a metal.
In this composite structure, at least either the first or the second member may be a corrosion-resistant, heat-resistant or abrasion-resistant member.
In this composite structure, one of the first and the second member may be a corrosion-resistant, heat-resistant or abrasion-resistant vane structure, and the other may be a vane holding member of a metal, and the first and the second member may be assembled by fitting one into the other to form a runner or an impeller.
In this composite structure, one of the first and the second member may be a decorative member and the other may be a holding member of a metal or a nonmetallic material.